1. Field of the Invention
The present disclosure relates generally to imaging systems, and, more particularly, to a method for achieving accurate page margins on a media in duplex printers.
2. Description of the Related Art
In media printing environment, it is important to assure that printing onto a media is performed accurately, i.e., the printing onto the media is achieved with accurate page margins. For example, in an inkjet printer, if the media is not aligned with the printhead of the inkjet printer, the ink will not print on a media in a proper position, and a corresponding image may not be placed on the media in the proper position. To achieve accurate page margins, a media 10 is positioned in a print zone in a default position, such that, the image is placed on the media 10 with desired top, left, right and bottom margins, as shown in FIG. 1 (PRIOR ART). More specifically, the media 10 is positioned in the input tray between two edge guides 14. Alternatively, the media 10 is positioned in the input tray between one edge guide and a side wall. The edge guides 14 control the left-to-right position to get a desired left-to-right position 18 of the media 10 as the media 10 is picked from the input tray into a print zone, thereby, aligning the media 10 with a feed roller 16 of the inkjet printer, while ensuring that the media 10 is fed perpendicular to the feed roller 16. The edge guides 14 have no effect on the media 10 after it enters the print zone. A leading edge position of the media 10 is detected with an edge sensor to determine accurate placement for the desired top margin, and thereafter, the media 10 is imaged in the print zone.
Printing onto the media 10 with accurate page margins in duplex printers (capable of printing on both sides of the media 10 (without user intervention) involves additional issues of misalignment of the media 10 with the printhead of duplex printers. As shown in FIG. 2 (PRIOR ART), in a duplex printer, with center alignment of media 10, the positioning of the media 10 for a first side imaging, i.e., imaging on a first side of the media 10, is controlled as described with reference to FIG. 1. Thereafter, the media 10 is removed from a print zone and flipped over in a duplex imaging path before being returned to the print zone for a second side imaging, i.e., imaging on a second side of the media 10, when fed perpendicular to the feed roller 16. During the flipping of the media 10, the media 10 may shift from a desired location, resulting in misalignment of the media 10. The misalignment may be to the left or right of the desired location of the media 10, or it may be angled relative to its desired location. The media 10 has to be aligned with the printhead of the duplex printer to achieve accurate page margins in second side imaging of the media 10.
Accordingly, in the prior art, several approaches have been used for alignment of media 10 for achieving accurate page margins during second side imaging in a duplex printer. These approaches utilize the repositioning of the media 10 to the desired location by moving the media 10 towards or away from a reference edge/wall. For example, the media 10 is aligned by applying a force 24 (referred to as an alignment force) to push the media 10 against an alignment wall 34 to reposition the media 10 to a desired left-to-right position 38 of the media 10. The alignment wall 34 ensures that the position of the media 10 is not shifted to an unacceptable amount during flipping. However, during this alignment process, the alignment force may be large enough to cause the media 10 to be stressed, and consequently the media 10 may be damaged during alignment. On the other hand, the alignment force may be small enough not to result in a proper alignment of the media 10 against the alignment wall 34. Moreover, the limitations on the alignment force restrict how far the media 10 may be pushed, thereby, limiting the media widths for duplex printing to standard sizes, such as, A4 size and Letter size that need very little left-to-right movement to contact the alignment wall 34.
None of the conventional approaches used for alignment of a media with a printhead of a duplex printer for achieving accurate page margins during second side imaging have successfully addressed the misalignment issues due to media damage, associated hardware costs, and limitations in media widths.
Accordingly, what is needed in an approach providing a method for achieving accurate page margins on a media in a duplex printer, while eliminating the issues of media damage and reducing associated hardware costs and limitations in media widths.